In: Electrical Engineering
With the aid of an appropriate circuit, explain the use of
potential dividers for
measuring AC high voltages as the measuring method.
Potential Divider is a method to measure High Voltage AC , High Voltage DC & Impulse Voltages.Potential Dividers works by obeying Voltage Divison rule.
below is the basic circuit diagram of a potential divider for HV AC Measurement.
Potential dividers can be classified into 3 types as :
1. Resistive Potential Dividers.
2. Capacitive Potential Dividers.
3. Mixed RC Potential Dividers.
Here For explanation purpose i am using Resistive Potential Divider circuit (page 2)
While measuring High Voltage AC, due to a sudden opening or closing of a switch or circuit breakers there may be ultra short duration transient voltage produced in the system called switching surges.
Due to presense of such switching surges our basic resistive potential divider circuits may burn or CRO/Measuring meter may be spoiled.Hence we need to modify the circuit with proper compensation.
To prevent the flashover votage we will use voltage controlled capacitors in parallel to Resistors R1 & R2 as shown below (Page 3)
Proper selection of of capacitor values are needed fro perfect compensation otherwise circuit wil be either overcompensated or under compensated.
For perfect compensation
if perfect compensation is done then modified attenuation factor is given as (page 4) -
By plugging in values of unknowns we can measure the desired AC Voltages.
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